compuwiz1937

iTrader: (17)

Here's the story: I swapped a rear end from an 84 Z28 that has 3.73 gears in it, my stock rear end had 3.23 gears so my speedometer is off about 10mph. According to transmissioncenter.net I needed a 15 tooth drive gear (gray) and a 43 tooth driven gear (purple) to correct the speedometer. I found the GM part numbers on the TCI web site and a local dealer had both gears. When I started the swap today when I got the driven gear assembly out I noticed the gear didn't look the same. I went back to transmissioncenter.net and further down page I found a section about the gears for the electronic speedometers. The driven gear I bought was for the cable driven speedometers. I couldn't find any information here or anywhere else about the gears for the electronic speedometers. I called another local dealer and the guy I talked to managed to find two different 43 tooth driven gears in the parts catalog but it didn't have any pictures. He put the order in for both of them so sometime next week when they show up I can go and have a look at them and see if they're what I need.

My question here is: on the transmissioncenter web site in the section with the electronic speedo gears, they talk about two different kinds of speed sensors, one for 35 to 39 tooth and one for 40-45 tooth driven gears. The dealers couldn't find a difference in the parts catalog, so am I going to have to buy this thing too??

Sorry for the incredibly long post, but I figured it'd be best to make a new thread instead of bumping an old thread not about this.

Pat Hall

iTrader: (31)

I ran into the same deal with the cable style speedo gears when I went to the dealership. They said the 40-45 tooth gears require a different sleeve/shaft assembly than the 35-39 tooth gears for some reason. I don't know if the shaft that the gear goes on is a different diameter or what. I have both style sleeves, and I can't visibly see a difference between the two. Maybe if I actually measured them with a set of digital calipers I might be able to tell a difference. With the electric units, the shaft is part of the electrical sender, so I guess you have to use the different sending unit for the same reason you have to use a different sleeve/shaft assembly for the cable style gears. It's also correct that you have to use the gray 15 tooth gear on the output shaft of the transmission instead of the red 17 tooth gear. The red one works for 3.23 and down, the gray one works for 3.42 and up.

Pro Built Automatics

There is the normal speedometer gear setup, and the early electronic gear setup. Both used the same drive gear on the output shaft, the difference is the driven gear. The early uses the gear with the shaft as part of the driven gear, and the later one the gear sits on a steel shaft. The early used two different housings, one to hold the 34-39 teeth, and one to hold the 40-45 teeth driven gear. The later gear changed in teeth count only. You will need to know which one you have to buy the right 43 tooth gear for this.

Pat Hall

iTrader: (31)

Huh. I guess I got hosed for a sleeve I didn't actually need in that case then since my original sleeve was a metal shaft too. I knew that the T5 trannies had an all plastic style speedo gear as well as the one with a metal shaft, but I didn't know the 700r4's ever used an all plastic one as well. I'm glad someone finally explained the difference to me on this. Thanks PB!

compuwiz1937

iTrader: (17)

I thought I was supposed to be using the red gear on it now, but I looked after I got the speed sensor out of the way, and the yellow 19 tooth drive gear is on it now. Since the driven gear was brown it has 39 teeth. According to the TS site I should have had the 17 tooth drive gear and a 45 tooth driven gear.
----------
Yeah, those are the gears I need.



So when you say the later gear changed in teeth count only, are you saying that my speed sensor is fine?

Pat Hall

iTrader: (31)

Yeah, from the way Pro-Built explained it, as long as you have metal shaft witht the D-shaped notch on the end, all those gears you posted in the picture above should work just fine on your sensor regardless of the tooth count. Btw, I've never even heard of a yellow, 19 tooth drive gear. You are talking about the gear on the transmission output shaft right? If so, the only ones I've ever seen are the gray 15 tooth and the red 17 tooth. Red is for 2.73-3.23, gray is for 3.42, 3.73, and higher. Like I said in my earlier reply, apparently I got hosed by the dealer when I bought another "sleeve" for my cable driven speedo since I already had the metal shaft with the D-shaped notch.

compuwiz1937

iTrader: (17)

I guess I'll find out soon enough Even if it does need to be changed it won't be such a huge deal since that piece is relatively easy to get to. The dealership I bought the original gears from was closed yesterday for some reason so I couldn't return the driven gear. I also want to try and exchange the drive gear because it has a little extra plastic around the teeth and I don't want any problems with little pieces of plastic in my transmission.